The present invention relates in general to an improved plug device for sealing an internal tubular passageway in a predetermined location against pressure and flow applied from either side. More particularly, the invention relates to a remotely installable and removable completion plug for pipeline hot-taps.
Two very common problems in the currently available pipeline plugs are that they often mar the bore of the pipe and they cannot hold high pressure from both directions. Another common problem with currently available pipeline plugs is that they are difficult to remotely install or remove. There are a number of applications for pipeline plugs, either land-based or underwater, which cannot be directly serviced by personnel, such service being performed by robots or by personnel working from some distance utilizing submersible craft with remote manipulators. One limitation of robots and remote manipulators is that they cannot reliably or efficiently perform fine mechanical maneuvers such as tightening sets of screws or bolts.
A large variety of plugging means exists for application as packers in wells, and some of this technology has been adapted to use for pipeline plugging. These devices typically use tapered wedges sometimes referred to as slips to grip the bore of the pipe and compress rubber seal rings with rectangular cross sections to provide sealing. Examples of this type of plug are the HydroTech Systems Hydroplug, the Thaxton plug, and T. D. Williamson, Inc.""s Wedge-Lock Pipe Plug. This type of plug does avoid having the seal scrubbed against the bore of the pipe while the plug is being shifted within the bore of the pipe. However, the gripping wedges tend to distort or mar the bore of the pipe, particularly when high pressures are retained by the plug. Pressure in one direction tends to tighten the wedges, while pressure in the other direction tends to loosen the wedges. Thus, these wedges are suitable for retaining pressure from only one direction.
A second type of plug is exemplified by T. D. Williamson, Inc.""s Lock-O-Ring plug. This plug has a external circumferential latching groove and an O-ring on a short cylindrical body. The plug is landed inside a prepared flange or body which has an internal circumferential groove containing a split latching ring recessed into that groove and shaped to be forced into engagement with the plug groove while still being partially engaged in the flange or body groove. In order to engage the plug groove, the latching ring is caused to distort to a smaller diameter by means of screws which are mounted in multiple equispaced threaded radial holes in the flange or body groove with their tips engaging the outer diameter of the latching ring. Screwing the screws inwardly causes the latching ring to engage the groove of the plug. A ball check valve which may be opened by insertion of a pin to displace the ball from its seat is provided to permit pressure equalization across the seal of the plug. The disadvantages of this type of plug are a tendency to cock in the bore into which it is installed because of its short length and the variations in O-ring friction against noncircular bores. A further disadvantage is the tendency of the radial screw holes to leak and a need for access to the heads of the screws for actuating or releasing the latching ring. This type of plug is particularly difficult to remotely install or remove.
Thus, a need exists for a plug suitable for sealing a bore that can easily be installed or removed by robots and remote manipulators.
A further need exists for a passive bidirectional seal having significant preloading contact with the bore, which is not scruffed during its installation.
The invention contemplates an improved plug device for sealing an internal tubular passageway in a predetermined location against pressure and flow applied from one side. The plug is selectively inserted and retrieved from one direction by means of a mandrel. The plug is latched into a prepared internal groove in the tubular passageway. The seal of the plug is manipulated in order to cause it to recess during installation and retrieval in order to avoid scuffing.
One aspect of the present invention is a sealing plug for selectively plugging a tubular flow passage, either temporarily or permanently, comprising: (i) a body assembly; (ii) a sealing assembly having an annular elastomeric seal; a static seal end, bonded to a one end of the elastomeric seal on an inner side of the static seal end and anchored to the body assembly on an outward side of the static seal end; and a movable seal end, bonded to a second opposed end of the elastomeric seal, wherein when said movable seal end is displaced in a direction going away from the static seal end the elastomeric seal is tensioned and when the movable end is moved back towards the static seal end the tension on the seal is relaxed; (iii) a reciprocable piston housed within the body assembly and connected to the movable seal end, said piston movable between a first position and a second position, wherein when said piston is in the first position the elastomeric seal is tensioned and when the piston is in the second position the elastomeric seal is relaxed; and (iv) means for moving the piston between the first and second position.
In accordance with a second aspect of the invention is a completion plug for a hot-tap fitting having: (i) a cylindrical body assembly; (ii) an elastomeric seal assembly consisting of an annular seal with an anchored end and a moveable end, wherein when the moveable seal end is moved to a first position the seal is stretched and when the movable end is moved to a second position the seal is relaxed; (iii) means for reciprocably moving said movable end between the first and second position; (iv) a plurality of radially extensible latch dogs housed within the body assembly, wherein said latch dogs are retractable to an inside position within the body assembly and extendable to an outside position wherein a portion of the latch dogs extend outside of the body assembly; and (v) means for moving the latch dogs radially between the inside and outside position.
In accordance with a third aspect of the invention is a tool for installing/retrieving a plugging device into a tubular passage. The tool comprises (i) a cylindrical stinger configured to fit within the bore of the sealing plug, said stinger having an elongated body with multiple flow ports, wherein each flow port selectively communicates pressure to a corresponding flow port in the bore of the sealing plug; (ii) means for selectably securing said annular stinger to the sealing plug; and (iii) means for guiding the sealing plug attached to the stinger into position in the tubular flow passageway.
In accordance with a fourth aspect of the invention is a plugging device for a hot-tap fitting comprising: (a) a cylindrical sealing plug having (i) a cylindrical body assembly having a concentric blind bore; (ii) an elastomeric seal assembly consisting of an annular seal with an anchored end and a moveable end, wherein when the moveable seal end is moved to a first position the seal is stretched and when the movable end is moved to a second position the seal is relaxed; (iii) means for reciprocably moving said movable end between the first and second position; (iv) a plurality of radially extensible latch dogs housed within the body assembly, wherein said latch dogs are retractable to an inside position within the body element and extendable to an outside position wherein a portion of the latch dogs extend outside of the body element; and (v) means for moving the latch dogs radially between the inside and outside position; and (b) an installation tool for installing or retrieving the sealing plug in a tubular flow passageway comprising (i) a cylindrical stinger configured to fit within the bore of the sealing plug, said stinger having an elongated body with multiple stinger flow ports, wherein each stinger flow port selectively communicates pressure to a corresponding bore flow port in the bore of the sealing plug; (ii) means for selectably securing said stinger to the sealing plug; and (iii) means for guiding the sealing plug attached to the stinger into position in the tubular flow passageway.
Yet another aspect of the invention is a process for sealing a tubular passageway against pressure and flow, said process comprising:
(a) selecting the tubular passageway to be sealed by a sealing plug, said sealing plug including (i) a cylindrical body element having an interior concentric blind bore; (ii) a seal assembly consisting of an elastomeric annular seal with an anchored end and a moveable end, wherein when the moveable seal end is moved to a first position the seal is stretched and when the movable end is moved to a second position the seal is relaxed; (iii) means for reciprocably moving said movable end between the first and second position; (iv) a plurality of radially extensible latch dogs housed within the body element, wherein said latch dogs are retractable to a retracted position within the body element and extendable to an extended position wherein a portion of the latch dogs extend outside of the body element; and (v) means for reciprocably moving latch dogs between the extended position and the retracted position;
(b) attaching an installation tool to the sealing plug, wherein the installation tool comprises (i) a cylindrical stinger configured to fit within the blind bore of the sealing plug, said stinger having an elongated body with multiple stinger flow ports, wherein each stinger flow port selectively communicates pressure to a correspondinng bore flow port in the blind bore of the sealing plug for controlling the means for reciprocably moving the moveable seal end and the latch dogs; (ii) means for selectively securing said annular stinger to the sealing plug; and (iii) means for guiding the sealing plug attached to the stinger into position for sealing the tubular flow passageway;
(c) moving the movable end of the elastomeric seal to the first position, thereby stretching the elastomeric seal;
(d) inserting the sealing plug into the tubular passageway while the elastomeric seal is stretched and the latch dogs are in the retracted position;
(e) moving the latch dogs to the extended position to bias against and engage an interior surface of the tubular passageway; and
(f) moving the elastomeric seal to the second position to relax the seal to bias the seal against the interior surface of the tubular passageway.
The foregoing has outlined several aspects of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed might be readily utilized as a basis for modifying or redesigning the structures for carrying out the same purposes as the invention. It should be realized that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.